1. Field of the Invention
The present invention is an improved leaf valve containing a normally closed lumen which, when affixed to the interior surface of a chamber defined by a surrounding envelope such as an intragastric balloon and fully extended, as for example, by the passage of a tube or catheter through the lumen, provides a direct path to the interior of the chamber. When the tube or catheter is withdrawn from the valve, the lumen of the valve stem folds on itself, accordion style, to positively close the lumen and prevent leakage from the chamber.
2. Background of the Invention
Implantable devices requiring external access to an interior chamber are well known in medicine. Tissue expander devices, for example, comprise an inflatable envelope of a biocompatible elastomer. Following surgical implantation beneath the skin, the device is gradually inflated by injection of a fluid into the chamber of the device through a self-sealing septum. As the implanted device gradually expands, it causes the overlying skin to stretch thus generating a flap of skin which may be used for reconstructive surgery.
A similar device is the intragastric balloon used to treat patients suffering from morbid obesity such as described by Garren et al in U.S. Pat. No. 4,416,267 and by Weiner et al in U.S. Pat. No. 4,694,827. Such devices are inserted empty, usually by means of an endoscope, into the stomach. Following deployment of the device within the stomach, the balloon is usually inflated by injecting a fluid into the interior chamber of the balloon through a catheter. When the balloon is fully inflated, the intubation catheter is removed by pulling it free of the balloon and out through the mouth. When the tube is pulled out of the balloon through a leak-proof valve, the balloon must remain fully inflated in the stomach for months. If the valve leaks, the balloon may pass through the stomach into the intestine where serious bowel obstruction may occur. The design of the valve that seals the envelope of such a balloon upon withdrawal of the inflation tube must provide a positive seal under a variety of pressure differentials.
Leaf valves are well known in the art (Andrews, MM, U.S. Pat. No. 2,700,980; MacDonald, W.W., U.S. Pat. No. 1,702,974). Their principle of operation and use is similar to flap valves. In general, they are used to seal a conduit through a surface across which a differential pressure exists thus preventing transport of fluid from the high pressure side to the low pressure side.
While flap valves are molded from an elastomer to fit snugly against the surface to be sealed, leaf valves are affixed to the surface so that the conduit passing therethrough the lumen is substantially parallel to the direction of travel of a catheter passed through the leaf valve.
Leaf valves, unlike flap valves, possess a conduit or lumen passing throught the stem, the walls of which are comprised, at least in part, of an elastomeric material. External pressure on the stem walls forces the elastomeric material to close upon itself thus effectively sealing the conduit. In other words, a positive seal is only possible when the pressure outside the stem wall is sufficient to deform the walls inward to close the conduit.
An improved curling or pig-tail leaf valve has been described (U.S. Pat. No. 4,775.379) by Terence M. Fogarty, in which two strips of elastomer, one of which is initially stretched, are molded together to form a stem leaving a conduit down the length of the valve stem. When the stem is removed from the mold, it curls up due to the difference in tension of the forming parts. When the stem curls up, it closes the conduit by pressing the walls together continuously along the length of the valve stem. The curling leaf valve has the advantage that it is more resistant to leakage in the absence of a pressure differential but it still requires a pressure differential for positive sealing. Thus, a valve is needed which will positively seal without the absence of a pressure differential. The difference between the self-kinking valve of the current invention and prior art valves can be viewed instructively by drawing an analogy to stopping the flow of water through a garden hose: prior art valves are analogous to stepping on the hose to stop the flow of water therethrough while the valve of the current invention stops the flow by kinking the hose.